Amplification by coherent addition of a pulse train using an enhancement cavity has been proposed theoretically. See B. Couilland, et al., “High Power CW Sum-Frequency Generation Near 243 nm Using Two Intersecting Enhancement Cavities,” Opt. Commun. 50, 127-129 (1984); see also R. J. Jones, et al., “Femtosecond Pulse Amplification by Coherent Addition in a Passive Optical Cavity,” Opt. Lett. 27, 1848-1850 (2002); both of these publications are incorporated herein by reference in their entirety.
More recently, addition of a relatively small number of picosecond pulses (approximately 100 pulses) has been demonstrated independently by two research groups. E. O. Potma, et al., “Picosecond-Pulse Amplification with an External Passive Optical Cavity,” Opt. Lett. 28, 1835-1837 (2003); Y. Vidne, et al., “Pulse picking by phase-coherent additive pulse generation in an external cavity,” Opt. Lett. 28, 2396-2398 (2003); both of these publications are incorporated herein by reference in their entirety.
In this approach, the pulses are extracted from the cavity by the use of an active switching device (i.e., an acousto-optic modulator, AOM). Therefore, the duration and central wavelength of the amplified pulse is not altered in this process. A major shortcoming of this approach as applied to short pulses is the difficulty of constructing an enhancement cavity with sufficiently small dispersion for sub-picosecond pulses. Furthermore, the amplification factor is limited by the finesse of the cavity.
Optical parametric amplification is another well-established amplification technique suitable for a range of wavelengths. See R. A. Baumgartner, et al., “Optical Parametric Amplification,” IEEE J. Quantum Electron QE-15, 432-444 (1979), which is incorporated by reference herein in its entirety. Application of the well-known chirped-pulse-amplification technique to parametric amplification was developed in the early 1990's. See A. Dubietis, et al., “Powerful Femtosecond Pulse Generation by Chirped and Stretched Pulse Parametric Amplification in BBO Crystal,” Opt. Commun. 88, 433-440 (1992), which is incorporated by reference herein in its entirety.
This so-called parametric chirped-pulse amplification (P-CPA) has received attention recently. See. J. Collier, et al., “Evaluation of an Ultrabroadband High-Gain Amplification Technique for Chirped Pulse Amplification Facilities,” Appl. Opt. 38, 7486-7493 (1999); see also I. Jovanovic, et al., “Optical Parametric Chirped-Pulse Amplifier as an Alternative to Ti:Sapphire Regenerative Amplifiers,” Appl. Opt. 41, 2923-2929 (2002); both of these publications are incorporated herein by reference in their entirety. A major advantage of parametric chirped-pulse amplification is that single-pass gains on the order of 107 can be obtained.